I totally agree with you.
The majority of the Teams at the Tour ride (bc sponsored) Shimano power meters. So I guess the miscalibration is an already build in feature 
Besides that: If individuals / teams go to an incredible extend to get illegal substances in their blood, faking a few numbers / miscalibrating a power meter would be not be the thing that stops them. And we talk just about a few % - that’s probably within the normal range of deviation of a power meter anyways. Not that I really know how doping works, but isn’t it less about power and more about how quick you recover?